Alexandra Castor and the Curse  of Slytherin
by Anirandom
Summary: Separated from her brother shortly after birth Alexandra Castor grew up in a normal wizarding family, that is until she goes to Hogwarts and meets her twin. Trying to keep her abilities hidden she finds this difficult since someone is trying to expose her
1. Chapter 1

**A/N: So I've been rereading the series and one thought stuck in my head: What if Voldemort had a twin sister? So here's what came out of that thought. Every person place or thing you recognize belongs to J.K. Rowling and I'm not making anything except entertainment from this.**

It was a cold rainy night at Hogwarts, Professor Dumbledore had just led in two lines of frightened first years who were all looking around the Great Hall in amazement save for two. A small, dark haired boy was staring at the Slytherin Banner hanging from the wall and the girl next to him was doing her best to feign interest in _anything_ to ignore the boy. Albus looked at the twins who he deemed similar but strikingly different in ways. After all, the little girl who had been named Aliana Riddle by the twins' mother had been adopted as an infant and had her name changed to Alexandra Castor. Turning to the Head Table Albus saw Horace Slughorn watching the twins with interest. No doubt he had noticed their similarities.

Clearing his throat Albus sighed "Alright, when I call your name, come up, I'll drop the Sorting Hat on your head, and you'll be sorted into your houses." The students at the house tables turned to look at the first years murmuring to their each other that this year's batch better be up to snuff. Albus unrolled a long scroll and pushed his glasses up his crooked nose. "Adams, Andrew" A tanned blonde haired boy walked up

"Hufflepuff!" The Hat called out, a table filled with students with yellow trim on their robes burst out in applause Andrew ripped the hat off, ran towards the table, and sat down glad to be out of the other student's line of sight.

"Black, Alphard"

"I can speak to snakes you know" Tom Riddle told Alexandra "And make things move without touching them."

"Big deal" Alex muttered 'God this idiot won't shut up… I mean honestly Da told me to keep my head down, that speaking to snakes and hearing their replies isn't natural…' Reaching up she grabbed a pendant around her neck and ran her thumb over it absent-mindedly,

"Slytherin!" The hat yelled, this time the table with students with green trim applauded as the dark haired boy walked to their table

'I should have listened to Grandfather… gone to Durmstrang where they like the Dark Arts… I wonder if I could transfer… I'll send mum and dad an owl.' Alex rubbed the necklace in thought as she stared around the Great Hall. Stuck in her own thoughts Alex didn't pay attention to the sorting until the boy next to her gave her a push.

"Alexandra Castor, are you here?" Professor Dumbledore had his eyes fixed on Alex as he called her name.

"Sorry" Alex muttered as she walked up, sat down, and had the hat dropped on her head. Luckily it was large enough to fall over her eyes so she couldn't see the people staring at her.

"I see. I see… a descendant of Slytherin. I've not seen one of his in over a century… but this one is different… plenty of loyalty- not usually seen in one of Salazar's descendants, courage, and a thirst for learning… normally I'd place you in Slytherin but with your other traits you would do well elsewhere as well…' The hat mused 'Ah there it is, your predominate trait, courage. Though you knew you would do well at Durmstrang where they appreciate the Dark Arts -like you being a Parselmouth- you still came here… well I've seen all I need to. You won't have an easy time Aliana Riddle but choose your friends well and you will do fine.' The hat's voice disappeared from Alex's head before yelling out loud "Gryffindor!"

Sighing in relief that her sorting was done Alex took off the hat, handed it to Professor Dumbledore, and proceeded to walk towards the far left table where the students wore red trim. Sitting down near the front of the table near a girl with dark hair pulled back into a taut braid she sighed and relaxed a little.

"Hi, I'm Septimus Weasley! Welcome to Gryffindor" A red headed boy a couple years older than Alex reached over to shake her hand, knocking over his empty goblet in the process.

"Sep, I see you're still as clumsy as ever" The dark haired girl chuckled looking up from her book.

"And you've still got your nose jammed in a book Minerva" Septimus grinned "Don't worry about Minnie over there Alex, she's a shoo in for prefect in three years but she's not so bad" Alexandra shook his hand and smiled slightly. The sorting went on- Gryffindor gaining new members in boys named Jeremy Davies, Jackson Erikson, and Alger Longbottom who insisted on being called Algie, and girls named Erica Dennit, Augusta Longbottom- Algie's twin- and Pamela Morgan.

After a few minutes of sorting that the new First Year Gryffindors didn't pay attention to Dumbledore- who they learned from Minerva was their Head of House- called "Tom Riddle"

"I saw him on the train. He's a weird guy isn't he?" Sep muttered

"You were standing by him in line Alex, he say anything to you?" Algie frowned

"Yeah… he's a Parselmouth and proud of it." Alex frowned

"Slytherin for sure then. That's the mark of a dark wizard. Salazar Slytherin himself was one too." Pamela frowned

"Yeah" Augusta frowned

"SLYTHERIN!" The hat yelled as soon as it touched Tom's head.


	2. Chapter 2

**A/N: Well here's chapter two, just kept writing and writing and here we are again.**

"I told you" Pamela frowned "This is not good. Seriously they let a Parselmouth in?"

"He's got to be related to the Gaunts… they're the only Parselmouths left." Algie frowned "Granddad told us didn't he Augusta?" He turned to his twin

"Yes…" Augusta frowned "But they've all married their siblings so he can't be a Gaunt."

'Keep you head down Alex, don't let on that you're a Parselmouth' Alex sighed as she thought of her grandfather's words.

"There was that one that ran away. The girl… they found her body in London." Sep frowned "Don't your cousins live near there Minnie?" He looked at the bespectacled girl who was still reading silently

"I'm not getting into this." Minerva muttered turning a page

Finally the sorting ended with Amadeus Zephyr going to Hufflepuff. Headmaster Dippet- an old, nearly bald man with a wispy beard clapped his hands together as Professor Dumbledore moved the stool and hat to the side before walking to the head table, and sitting at Dippet's right hand side. "Let the feast begin!" Dippet called, food appeared all around the tables.

"Feast looks good this year, eh Min? Min? Minnie Mouse look up! Food's here!"

"Don't" Minerva slammed her book on the table with a thud "call me that" she growled, her emerald colored eyes flashing behind her glasses. A twinge of a Scottish accent appeared in her words as she glared at Sep.

"Sorry, sorry" Sep grinned at his friend

"Food looks good" Minerva looked around at the table. Septimus banged his fist on the table with a quiet growl. The cluster of first years grinned and chuckled as they watched the two second years bicker.

"Hey Alex, can you pass the green beans?" Algie spoke up looking around at the food.

"Sure" Alex handed him the bowl, Algie dumped a generous amount of the green vegetable onto his plate.

"Thanks Lex" He muttered as he stuffed a bite into his mouth.

"No problem" Alex shrugged as she speared a baked potato with a knife and dumped it on her plate before Septimus offered her a plate of roast. "Thanks" She took the plate and placed some roast on her plate before offering it to Algie.

"Thanks Lex" Algie grinned, Alex shrugged

"So Alexandra Castor, what shall your nickname be? We have Minnie, Sep, and Algie, hmm Alex doesn't fit too well… how about Zandra?" Sep grinned

"Zandra Castor… I like it" Zandra nodded swallowing a bite of roast

"Hey Zandra, pass the peas will ya" Jackson spoke up for the first time.

"Yeah, sure" Zandra picked up a bowl full of steamed peas and handed them to the blonde haired boy.

"Thanks" Jackson nodded

"No problem" Zandra shrugged, the Gryffindors continued eating until their dinner vanished and turned into dessert. Zandra's eyes widened as she looked around, ladling some Apple cobbler onto her plate she ate it slowly and looked around. The boy she had met before the sorting was sitting at the Slytherin table eating a bit of everything he could get his hands on.

"That Riddle boy will be trouble… I can feel it…" Sep frowned

"I second that" Zandra muttered as the boy looked up and stared at her with one brow quirked as if he was saying 'What are you looking at?' he looked strangely pleased with himself as he sat in between two burly looking boys.


	3. Chapter 3

**AN: Well here's chapter three, and the longest chapter yet!  
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For Zandra and her friends the night passed quickly and soon they were finishing up dessert. Septimus joked all the way there with Minerva rolling her eyes every few minutes. Zandra however was deep in thought as she scribbled out a short letter to her parents

_Hey Mum Dad and Granddad,_

_Sorting went fine I'm in Gryffindor! Met this weird kid named Tom Riddle on the train… he claims he's a Parselmouth… is that even possible? So far my housemates seem alright. I haven't met all of them but Septimus Weasley- a second year- is a bit of a goofball but good for morale, and then there's Minerva McGonagall- another second year- is a shoo in for prefect according to Sep- always has a book with her. The Gryffindors in my year are Alger- Algie- Longbottom, his twin sister Augusta, four other boys named Jeremy Davies, Jackson Erikson, Matthew O'Flarrety, and Jonathan Perry. The other girls I'll be rooming with besides Augusta are Erica Dennit, Arlene Masters, and Pamela Morgan. The feasts are good, like you remember, and I don't know what's for breakfast tomorrow. Well that's it for now. I love you guys, _

_Zandra_

Looking around Zandra sighed 'I'm gonna have to find the owlery…'

"Hey Zan, I'll take you to the owlery after dinner, just let me get the password for the Fat Lady from one of my brothers." Sep grinned seeing Zandra's note. "Hey Tertius, what's the password to the Fat Lady? I'm gonna take Zandra here to the owlery"

"It's Bubotuber" Tertius- another redheaded Weasley stared at Septimus

"Okay thanks Tertius!" Sep grinned

"No problem, don't get caught out too late" Tertius shrugged

"We won't" Sep turned to Zandra "You done Zandra?"

"Yeah" Zandra swallowed her last bite of cobbler.

"We're all named so our father can remember what order we're in, there's Primus- who's head boy, Secundus, Tertius, Quartus, Quitus, Sextus, and me- Septimus." Sep rolled his eyes "I wish they were a bit more creative."

"Could be worse, Alphard Black perhaps?" Alexandra chuckled as they walked down towards the doors.

"Very true" Sep laughed "This way, we'll have to be quick."

"Got it, Covert Operation" Zandra grinned

"Yep" Sep nodded, the two ran down the halls, Zandra constantly looking around as they went. "Okay owlery is up this tower" Septimus started climbing the stairs. Zandra followed him up remembering every turn as they went. Finally when they reached the owlery a dark eagle owl flew over to Zandra.

"Hey Hades" Zandra stroked the owl's wing "Take this to mum and dad" she tied the message to Hades' leg. The owl nipped her finger affectionately and flew off. "Thanks for taking me here Sep, would never have found it on my own."

"You looked pretty spooked by the Riddle boy, is anything wrong?" Sep frowned, for once he was serious "You can tell me, hell you should see what Sextus pulls off if you're afraid I won't believe you."

"It's nothing" Zandra scratched her head "Just pre-term jitters"

"Ah, eh don't worry, they sort of take it easy the first week" Sep grinned "Now let's go, we don't wanna be caught out after hours"

"Yeah" Zandra nodded as they started walking to the common room

"We're going to want to watch out for the caretaker Hakan Munk. He's starting to slow down, at least his body is. Not his mind though." Sep muttered

"Hakan Monk… got it" Zandra nodded

"Let's go, if we make a run for it I bet we can reach Gryffindor Tower before lights out." Sep frowned as he thought

"Alright then" Zandra nodded

"Ready?" Sep grinned "Stay close on my heel"

"Got it, let's go" Zandra grinned.

"Alright then" Sep turned and started sprinting down the hall with Zandra close behind. Running past the ghost of a tall witch Zandra jumped to the side to prevent running through her.

"Sorry!" Zandra called over her shoulder

"You okay?" Sep turned

"Yeah, nearly ran through a ghost." Zandra nodded picking up speed again

"Ah, yeah not to pleasant, for us or them. Sextus says it feels like having a bucket of cold water dumped through you." Sep shuddered as he jogged in place for Zandra to catch up. "Nearly there now, just gotta get to the moving staircase then up to the seventh floor."

"Alright" Zandra nodded as the duo burst out onto the landing

"Okay, watch your step, on some of these the middle step is just an illusion." Sep placed his hands on his thighs as he caught his breath as they waited for the staircase to arrive at the landing.

"Thanks, that's definitely something to remember." Zandra nodded

"You're quick, ya know that?" Sep grinned

"Thanks, played football in Muggle School." Zandra grinned as she stretched her arms up over her head.

"That stupid sport where you kick a ball across a field and can't use your hands?" Sep laughed

"Yeah, well my parents live in London, not many Wizard kids to play with" Zandra laughed as the staircase stopped in place.

"Oh wait until you see the first Quidditch match of the season" Sep started walking down the staircase with Zandra at his side.

"I've seen Quidditch games before, just never got to fly much, unless I was at my cousin's place in the country." Zandra shrugged

"Ah well we'll fix that. Secundus is Quidditch Captain, we'll teach you to fly no problem." Sep grinned

"Thanks Sep" Zandra smiled as they waited for the second staircase to arrive.

"Ah there you are Septimus, you haven't been doing anything against the rules have you?" Another red headed Weasley smiled at Sep.

"No Primus, I was just showing Zandra here where the owlery was. She had a letter for her parents." Sep shrugged

"Quick, get in the Common Room. Munk's on a rampage, someone set off some Filibusters in some toilets on the first floor." Primus sighed

"You know where Sextus is? Sounds like something he would do…" Sep sighed

"He was with me" Primus scratched his head before turning to Zandra "It's nice to meet you Zandra, welcome to Gryffindor."

"Thanks Primus, it's nice to meet you too." Zandra smiled

"Well let's go" Primus led the two to a portrait of an overweight witch

"Password?" The witch spoke up

"Bubotuber" Sep shot a grin at Primus "Tertius told us" the portrait swung open revealing a hole in the wall that led to a circular, red painted room.

"Get to bed Sep, Zandra the girls' dorms are up the right staircase. The First Year's dorm is labeled"

"Okay, thanks" Zandra nodded "Thanks for showing me the owlery Sep. 'Night"

"No problem, night Zandra" Sep grinned before walking up the staircase to the boy's dorms with Primus. Zandra walked up the staircase to the First Years' dorm, walked in, and quickly found her bed. Taking her shoes off she fell asleep fully clothed.


	4. Chapter 4

**A/N: Well here's chapter Four!**

Zandra woke up just as the sky was starting to turn pink sitting up in bed she looked around and yawned. 'Well classes will probably start today, better get up and get a good breakfast.' Kicking her legs over the side of her four poster bed she scratched her head.

"Hey Zandra, you awake?" Pamela said in a soft tone

"Yeah, I'm gonna get some food, you?" Zandra retorted shaking out her dark hair

"In a minute, I'm going to have to get changed" Pamela sighed "You go ahead though."

"Okay, I'll see you there Pamela" Zandra grinned

"See you" Pamela smiled as Zandra slipped her shoes on and tied the laces. Walking down to the Common room she saw Septimus playing chess with Minerva. From the look of the board Minerva was winning.

"Morning Minerva, Sep" Zandra sat down next to them

"Hey Zandra, you sleep well?" Sep grinned

"Yeah, how about you two?" Zandra looked from Sep to Minerva

"Great" Sep shrugged

"Me too" Minerva nodded as she made a move "Checkmate"

"What? How?" Septimus scanned the board "Oh… Good game Min" He grinned

"You too Septimus" Minerva chuckled as she put the black onyx pieces into her bag. "I'm going to breakfast, you coming Sep?" She grinned

"Yeah, are you coming too Zandra?" Sep turned to Zandra

"Oh yeah, I'm starving" Zandra nodded

"I hope we get some good subjects today…" Minerva muttered as they walked towards the door. "Oh, Zandra if the schedule hasn't changed you'll have Double potions first period and then Charms after this morning."

"You still remember our first year schedule?" Sep laughed

"Yes, don't you?" Minerva cocked a dark brow

"God, you never forget anything!" Sep grinned as Zandra ran back to grab her Potions book trusting Minerva's memory.

"Minerva says First years have Double Potions followed by Charms" Zandra opened her trunk and dug through it for her Potions and charms books." Grabbing them she stuffed them into her bag.

"Ah, thanks Zandra" Pamela called from the closed bed curtains

"No problem" Zandra retorted running back downstairs where Sep and Minerva were waiting for her.

"Were you grabbing your books?" Sep grinned

"Yeah" Zandra nodded

"I see you're learning to take advantage of Minnie's memory like we all do." Sep chuckled

"It's not taking advantage if I'm offering the information Septimus" Minerva rolled her eyes

"True…" Sep grinned as the three walked out the portrait hole and down a staircase.

"I hope we get some more… interesting plants in Herbology this year" Minerva spoke up when they reached the Great Hall

"I don't… Sextus spent a week in the hospital wing after an incident with an adolescent Mandrake." Sep winced at the thought but then turned to Zandra "Don't worry. You won't see anything _too_ dangerous in your first year."

"Great… that's great" Zandra gasped out, clearly relieved 'I hope Hades is back with a letter from mum and dad…'

"Honestly, none of the Professors will allow you to die" Minerva shrugged as they walked beside the Gryffindor table looking for seats. With a loud screech Hades swooped down and perched on Zandra's shoulder sticking one leg out for her to untie a thick letter wrapped around his leg.

"My god Hades, it looks like you've got a splint on that leg" Zandra chuckled as she picked the bird up, sat down at the table, and plunked Hades down next to her plate. Giving Hades a sausage link she turned to the knot keeping the letter in place and quickly untied it. Hades stared at the girl while Zandra ripped open the letter.

_Dear Zandra (by the way, the nickname fits),_

_First of all Congratulations on Gryffindor! Now about your question about this boy named Tom Riddle: to answer that I first have to tell you why you know no other Parselmouths. If you haven't already figured it out you were adopted as an infant. Your parents found you at Wool's Orphanage in London the day after you were born which was also the day your mother died. I honestly never bothered finding out her name but I'm looking into it now. You remember what I told you before you left on the train. Keep it in mind and tell _no one_ especially not Tom Riddle. I'm not telling your parents about this letter because they would come and drag you home in an instant. Write again soon and send a different letter to me if anything happens._

_Love, always_

_Granddad_

Reading the letter over twice Zandra nodded and placed it into her bag before loading her plate up with bacon, eggs, and toast. Eating quickly she sighed as Professor Dumbledore walked down the aisle passing out timetables. Looking at the one Dumbledore placed by her plate she couldn't help but grin: Minerva was right.

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><p><strong>End AN: September First in 1938 was a Thursday (looked it up) so that's why Zandra and her year mates will be having Double Potions on their first day of classes.**

**Next time on Alexandra Castor and the Curse of Slytherin: Potions Class with the Slytherins! Zandra and Tom stuck in a classroom together? With Gryffindor and Slytherin Houses' rivalry? Nothing good can come from this!**


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